1. Field of the Invention
The present invention generally relates to a damper mechanism and a damper disk assembly. More specifically, the present invention relates to a damper mechanism and a damper disk assembly for absorbing and attenuating torsional vibrations while transmitting torque.
2. Background Information
A clutch disk assembly used in a vehicle has a clutch function and damper function. The clutch function is provided to facilitate connecting to and disconnecting from a flywheel. The damper function is provided to facilitate absorbing and attenuating torsional vibrations transmitted from the flywheel. Generally speaking, vibrations on a vehicle include idling noises (rattling), driving noises (acceleration/deceleration rattling, droning), and tip-in/tip-out or low frequency vibrations. Part of the damper function of the clutch disk assembly is provided to prevent these noises and vibrations.
The idling noises relate to a rattling sound generated in the transmission that typically occurs when a driver shifts into neutral while waiting for the traffic signal to turn green, and releases the clutch pedal. The reason for this noise is due to a large torque fluctuation that occurs when the engine combusts as the engine torque remains low at the engine idling speed. At such a moment, the input gear and the counter gear in the transmission are subject to a tooth beating phenomenon.
Tip-in/tip-out or low frequency vibrations are due to a large body sway that occurs when the acceleration pedal is abruptly engaged and then released. When the rigidity of the drive train is low, a torque, which is transmitted to the tires, is fed backward from a tire side to the torque, and a backlash phenomenon results causing an excessive torque on the tires, which then results in a large transient forward/backward vibration of the body.
Concerning the idling noise, critical torsional characteristics of the clutch disk assembly are in the zero torque neighborhoods. The torque therein should be as low as possible. On the other hand, it is necessary to make the torsional characteristics of the clutch disk assembly as rigid as possible in order to suppress the forward/backward vibration in the tip-in/tip-out phenomenon. In order to solve problems mentioned above, clutch disk assemblies with two stage characteristics having two kinds of spring members have been provided. In such a design, the torsional rigidity and the hysteresis torque in the first stage of the torsional characteristics (small torsional angle region) are kept low in order to achieve a noise suppression effect when idling. Since the torsional rigidity and the hysteresis torque are set high in the second stage of the torsional characteristics (large torsional angle region), the forward/backward vibration in tip-in/tip-out phenomenon can be sufficiently attenuated. Furthermore, a damper mechanism is also known which effectively absorbs minute torsional vibration in the second stage of the torsional characteristics by means of preventing the second stage large friction mechanism from operating when minute torsional vibrations resulting from fluctuations of engine combustion are supplied.
As mentioned above, a spring member with a lower rigidity and a friction generating mechanism having a small friction resistance in order to have a lower torsional rigidity and lower hysteresis torque during a first stage (small torsional angle region) in the torsional characteristics are known. The friction generating mechanism is, generally, composed of a friction washer and a spring member for urging the friction washer against the hub in the axial direction. In this structure, the number of parts is increased and the structure becomes complicated. Furthermore, the space needed to accommodate the friction generating mechanism is large. In addition, the structure for securing a rotational gap to prevent operation of the friction generating mechanism corresponding to minute torsional vibration is complicated.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved damper mechanism or damper disk assembly that absorbs and attenuates torsional vibrations while transmitting torque. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.